The present invention relates to cylindrically-shaped bodies with a variable diameter.
Various types of cylinders, for example, are used in a printing press, including ink rolls, plate cylinders, blanket cylinders, and web-guiding cylinders.
German Patent No. 196 49 324 C2 for example purports to disclose a changeable-circumference rotating body for rotary printing presses having a shaft (element four) on which a cylinder-like support element (element eleven) for changing the circumference is supported. A cylindrical screw spring (element twelve) connected at one side directly or indirectly to the shaft is located about the support element. At the other side of the screw spring is a device for relative movement of the coils of the spring in the axial direction, in order to selectively change the diameter of the screw spring. The cylinder can be used as a blanket cylinder, a redirecting cylinder for a web with a suitable diameter for different paper thicknesses, or a flat drive belt roll to change the rotational rate of a drive.
Underneath the screw spring, springs (elements thirty-six and thirty-seven) force segments (identified by numbers thirty-one through thirty-four) against the truncated-cone-shaped rotating element. Axial movement of the rotating in direction F changes the diameter by moving the segments in direction A. Spaces still result in the outer circumference of both the screw spring and between the elements.
German Patent No. 1 097 452 purports to disclose a printing cylinder formed of a conically-shaped carrier cylinder (element twenty) and an inner-conical separable sleeve (element nineteen) for a rotary printing press with two interacting cylinders (elements eleven and twelve). A pressurized fluid in a screw-shaped groove (element twenty-five) acts to expand the sleeve to expand the sleeve for removal or to permit the sleeve pushed onto the carrier cylinder. The sleeve sits with a press fit on the carrier cylinder when pressure is not provided. The fluid pressure system is complicated and no device for axial movement is disclosed.
In printing presses where two cylinders in frictional contact with each other are driven by independent motors, it can be a problem that one motor operates at full torque and the other motor acts as a less than desirable torque or even as a brake. This unbalance is due to the fact that minor diameter differences between the cylinders can cause one cylinder to transmit torque to the other through the frictional contact.
An object of the present invention is to provide a variable-diameter cylindrically-shaped body in which the effective diameter can be easily changed. Another alternate or additional object is to provide better torque control for printing press cylindrical bodies. Yet another alternate or addition object is to provide for a cylindrical body with a solid outer surface with an easily-changeable diameter.
Commonly-assigned U.S. Pat. No. 6,110,092 discloses a roller having mantel with a pattern of openings for permitting a variable diameter. Inclined portions of the mantle interact with sliding portions to change the diameter. Openings are present on the outer surface. No tapered elements are disclosed.
The present invention provides a variable-diameter cylindrically-shaped body comprising a plurality of first tapered elements, and a plurality of second tapered elements interacting with the first tapered elements and movable axially with respect to the first tapered elements, the first and second tapered elements defining an outer surface of the body. The outer surface has an effective diameter variable as a function of axial movement between the first and second tapered elements.
Cylindrically-shaped as defined herein is a generally cylindrical outer surface, but need not be perfectly cylindrical. Preferably, a diameter of the outer surface does not vary by more than 10% from the minimum outer surface diameter.
Preferably, the first and second tapered elements are constructed so that as the tapered elements move with respect to each other the varying effective diameter of the cylindrical body is the same over the entire width of the cylindrical body. A rosette pattern may be formed when the tapered elements move away from a zero position.
Most preferably, contacting edges of the first and second tapered elements are such that the edges are in contact over their contacting surface for every diameter change caused by sliding movement of the tapered elements.
Preferably, the body is a rotating body, and most preferably a rotating body in a printing press.
Through use of the interacting first and second tapered elements, the effective diameter (the maximum diameter) can be changed easily, and an outer surface without openings can be provided.
The cylindrical body preferably is attached to a torque controller so as to alter or control the torque of a motor driving the body by altering the body diameter. The cylindrical body of the present invention can be, for example, provided in a press as a plate cylinder and a blanket cylinder, each with a variable diameter and driven independently by an individual motor. Varying the diameter of the plate and blanket cylinders can alter the torque experienced by the motors driving the two rollers so as to properly split the torque between the two motors. This configuration can aid in solving the torque-splitting problem present in presses where contacting cylinders are driven by independent motors.
The outer surface of the cylindrical body preferably has no openings, so that the body may be used, for example, as an ink form cylinder which can carry ink directly on its outer surface.
The cylindrical body alternatively may be used as a blanket, plate or other press cylinder, which can expand its diameter to permit easy removal and to firmly hold a tubular-shaped blanket, plate or other printing form sleeve at the outer surface.
The cylindrical body may have an outer slot, and a flat plate, flat blanket or other element may be wrapped around an inserted at both ends into the slot. The effective diameter may then be expanded to firmly hold the flat printing form.
The cylindrical body may also be used for contacting a web or signatures either directly or through an elastic element, such as a blanket. As such the body can act as a variable radius contact driven roll or driving roll having fine adjustment of a rotational speed or for varying a cut-off length. Moreover, tension in the web can be controlled in an out-feed or in-feed or in a span between two nips. The speed of the top and bottom web in a multi-web package also could be controlled.
When used for transferring fluids such as ink or wetting solution, the delivery of the fluid amount can be altered by changing the diameter.
Also, the variable diameter can cause the cylindrical body to move into or out of contact with another object, such as another cylinder, or can alter the contact pressure between the cylindrical body and another object.
The cylindrical body can be controlled by a controller controlling a diameter setting device, which moves the first tapered elements axially with respect to the second tapered elements. The setting device for one set of tapered elements may include a motor with a shaft having interior threading, and a second shaft with interior threading fixedly connected to the tapered elements. A clutch may be provided to permit the two shafts to rotate together when engaged, or to permit a setting operation when disengaged.
The present invention also provides a printing press comprising a first variable-diameter cylindrical body including first and second tapered elements facing each other.
Preferably, the press includes a second cylindrical body forming a nip with the first cylindrical body, a first motor for driving the first cylinder, a second motor for driving the second cylinder, and a torque controller for distributing torque between the first and second motors as a function of a diameter of the variable-diameter cylinder.
The first and second tapered elements preferably are constructed so that as the tapered elements move with respect to each other, an effective diameter of the cylindrical body remains similar over the entire width of the cylindrical body. A rosette pattern may be formed when the tapered elements move away from a zero position.
The first cylindrical body preferably is a form roll, plate cylinder or blanket cylinder of an offset lithographic printing press.
Preferably both the first and second cylindrical bodies have variable diameters.
The variable-diameter cylindrical body can also be used for lateral register control of a web by moving the first and second tapered elements in a same direction without altering the diameter.
The present invention also provides a method for altering a printing press rotating body effective diameter including the steps of varying an effective diameter of a cylindrical body by moving a plurality of first tapered elements axially between interacting second tapered elements, the first and second tapered elements defining an outer surface of the body.
The method may further include altering a torque of a drive motor for the cylinder by varying the diameter.
The method also may include altering ink or wetting solution delivery as a function of the diameter.
The method also may include securing a printing form, such as a blanket or plate, to the cylindrical body by altering the cylindrical body effective diameter.
In addition, the method may include controlling microslip in a nip, or controlling the speed of a web, the tension in a span between two nips, the tension in an out-feed or the tension in an infeed.
The method also may be used to move the cylinder into or out of contact with another roll or object or to adjust the contact pressure between the cylinder and another object.
Rather than changing the diameter, if each of the first and second tapered elements are independently driven, the method also could include moving the cylindrical body laterally by moving the first and second elements in a similar direction.
xe2x80x9cPrinting formxe2x80x9d as defined herein can be any element covering a printing press cylinder, including a blanket, plate, or roll covering.